The present invention relates to a method for correcting programs running on a computer, and, more particularly, relates to a method for correcting programs without discontinuing service provided by the programs.
By virtue of widespread use of the Internet, every computer became accessible substantially from all over the world. But, at the same time, it is expected that possibility of unauthorized access to computers may increase. As a protective measure against such situation, there are publicly released various patch files that prevent such unauthorized access to the computers. In the patch file, program correction information for correcting programs is recorded, and the unauthorized access may be prevented by using the patch file to correct the programs. The patch file may be applied to all programs running on the computer. For example, the programs running on the computer may include an operating system, applications and so on. A program correction procedure using the patch file is as follows: (1) discontinuing service; (2) applying the patch file and correcting the programs; (3) restarting the system; and (4) restarting the service. In order to correct the programs in such procedure, it is necessary to discontinue the service temporarily. It is because the operating system and the applications typically may not be corrected while they are running. Therefore, when the computer is operating, the correction procedure may be applied to the programs which are not active temporarily, and at the time of the next starting, the corrected programs may be used.
In the conventional program correction procedure, it is necessary to discontinue service temporarily to correct the program. Since new patch files for program correction are created frequently, if the service is discontinued every time the new patch file is created, quality of the service may be decreased. In one method, such frequent discontinuance may be mitigated by executing the program correction procedure for several patch files collectively. But considering the fact that unauthorized access to the computer may be made at any time from anyone unexpectedly, it is not preferred to postpone the program correction concerning security. One technology for correcting programs is described in Japanese Patent Application Laid-Open No. Hei 8-263279. In this document, a method is described for performing program correction without terminating programs running on logical computers in a computer system that has a mechanism for virtualizing computers and building a plurality of logical computers from one physical computer. But, in this method, the program correction may be performed not to the programs that are running on the logical computers, but to the control programs that control the plurality of logical computers centrally. Further, while the control programs are corrected, almost all programs on the logical computers are terminated. That is, the programs on the logical computers cannot continue service because they stop working. Still further, this method does not provide correction for the programs such as an operating system and applications that process the service on the logical computers.